Although nutrients may be provided by either parenteral or enteral routes, clinicians are making greater efforts to use the enteral route in light of research showing that enteral feeding confers certain physiologic benefits not seen with parenteral feeding. Published studies have reported that early enteral feeding provides energy and nutrients essential for optimal healing and immunocompetence, helps maintain the gut mucosal integrity, and may blunt catabolic effects and normalize blood glucose levels.
For optimal recovery, traumatized patients require proper nutritional intake. Proper nutritional intake is particularly critical for patients suffering from malabsorption conditions such as, for example, Crohn's Disease, short bowel syndrome, pancreatitis and other diseases and illnesses which cause malabsorption of essential nutrients. Lack of proper nutrition can result in malnutrition-associated complications, including prolonged negative nitrogen balance, depletion of somatic and visceral protein levels, immune incompetence, increased risk of infection, and other complications associated with morbidity and mortality. A primary objective of nutritional support for the traumatized person is to replace or maintain the body's normal level of nutrients by providing adequate energy substrates, protein, and other nutrients essential for tissue repair and recovery.
Appropriate enteral nutrition following injury may minimize malnutrition, provide nutrients to the immune system and maintain the gut epithelium, which acts as a barrier to translocation of bacteria. This may help prevent the development of sepsis. Malnutrition may compromise the immune system and contribute to septic complications. It has been reported that cell-mediated immunity is reduced in proportion to the level of malnutrition of the critically ill patient.
Persons suffering from malabsorption conditions are deprived of essential bodily fuels or their precursors thus compromising their nutritional status and more specifically, the integrity of the intestinal tract, especially during times of stress. Often, such patients are intolerant of dietary fiber. Patients suffering from malabsorption syndromes often have a diminished capacity to absorb water and electrolytes. This further challenges the nutritional status of the patient and may lead to dehydration.
To aid persons suffering from malabsorption conditions, enteral diets are desirably provided in an "elemental" state. Strictly speaking, an elemental diet would be one in which all components of the formulation are present in their simplest molecular state. For example, the protein source would be provided as amino acids. The carbohydrate source would be simple sugars. However, such compositions are difficult to formulate and are sometimes not well tolerated by the patient.
One difficulty in preparing products containing high levels of free amino acids is that such products will not form stable emulsions suitable for long term storage. Thus such products are only available in a powdered form requiring reconstitution prior to usage. Health care providers and ambulatory patients typically prefer products that are provided as a liquid and require no reconstitution. A further disadvantage of powdered products is that the high concentration of free amino acids are noted for their extremely objectionable taste. Unfortunately this objectionable flavor can lead to noncompliance with the feeding regimen in patients who would benefit from elemental diets. Examples of such patients include those suffering ulcerative colitis, Crohn's disease, short bowel syndrome, and pancreatitis. Noncompliance with a proper feeding regimen will eventually lead to malnutrition in these patients.
Examples of powdered elemental nutritional products, whose protein source is predominantly amino acids, are Vivonex TEN.TM., and Vivonex Plus.TM., and Stresstein.TM., all of which are manufactured by Novartis.
Further developmental efforts with elemental diets focused on preparing products that would form stable liquid emulsions so that the products could be sold as ready to feed liquid nutritionals, which are typically preferred by health care providers and patients. One way to formulate an "elemental" nutritional product that is stable for extended periods as a liquid, has been to utilize a protein system for the product which incorporates a hydrolyzed protein. Hydrolyzed proteins are desirable because they provide the nutritive equivalent of the original protein in the form of its constituent amino acids and peptides of varying lengths. One useful hydrolyzed protein has been found to be soy protein hydrolysate. However, nutritional products incorporating high concentrations of hydrolyzed soy protein do not yield stable products in the absence of an intact protein. Once a soy protein is hydrolyzed, it loses its primary and secondary structure and consequently some of its functionality, including emulsifying properties. For that reason, it does not have surfactant properties and is unable to stabilize a formulation which results in phase separation.
For example, U.S. Pat. No. 5,403,826 to Cope, et al., discloses a nutritional product for persons infected with HIV. This product includes a soy protein hydrolysate and a second source of protein which comprises a source of intact protein, in a quantity sufficient to yield a stable emulsification of the soy protein hydrolysate and the intact protein. This product does not yield a shelf stable product in the absence of the intact protein. Typically, the intact protein will be present in an amount from about 10% to about 30%. The product also includes a source of fat which is formed from a blend of canola oil, medium chain triglyceride (MCT) oil and fish oil. The '826 patent does not teach the desirability of incorporating a structured lipid into an elemental diet.
As another example, U.S. Pat. No. 5,514,655 to DeWille, et al., teaches an enteral nutritional product with a protein system containing soy protein hydrolysate and intact protein. Approximately, 50% to 90% of the protein system consists of soy protein hydrolysate and the remainder includes not more than 50% of one or more intact protein sources, such as sodium caseinate and whey protein concentrate. The system also includes an emulsifier selected from the group consisting of diacetyl tartaric acid esters of monodiglycerides and sodium stearoyl lactylate.
As still another example, U.S. Pat. No. 5,547,927 to Cope, et al., describes an enteral nutritional product for patients undergoing radiation therapy and/or chemotherapy. This product includes a protein system comprising, in a preferred embodiment, about 60% of a soy protein hydrolysate; about 30% of a whey protein concentrate; and about 10% of a pea protein isolate. This product also does not yield a shelf stable product, in the absence of the intact protein. Because the soy protein hydrolysate does not form a stable emulsion, an emulsifier is added. This product also includes a lipid system comprising MCT oil and canola oil.
One enteral nutritional product containing a protein system comprising a large percentage of hydrolyzed protein is described in U.S. Pat. No. 5,221,668 to Henningfield, et al. This patent discloses a nutritional product for trauma and surgery patients. The product comprises from about 18% to about 24% protein; from about 20% to about 30% lipids; and from about 46% to about 62% carbohydrates. The protein system includes from about 20% to about 35% lactalbumin hydrolysate, from about 60% to about 70% hydrolyzed sodium caseinate, and from about 8% to about 14% L-arginine. It does not include hydrolyzed soy protein.
Another liquid ready to feed product considered to be an elemental formula is currently available from Clintec Nutrition by the trade name Crucial.TM.. Its peptide system includes hydrolyzed casein, but it does not include soy protein hydrolysate. The lipid system includes marine oil, but the marine oil is not incorporated into a structured lipid. The carbohydrate system does not include sucrose.
Peptamen VHP.TM. is another nutritional product available from Clintec Nutrition that is considered to be an elemental product. The protein system is hydrolyzed whey, the lipid system does not include a structured lipid and the carbohydrate system does not include sucrose.
It has also been found to be beneficial to include a structured lipid as part of an enteral diet. Structured lipids have not yet been incorporated into elemental diets. Structured lipids are triacylglycerols containing mixtures of short-, medium-, and long-chain fatty acids attached to a glycerol backbone for specific functionality. Structured lipids are formed by (a) hydrolysis and esterification, (b) interesterification, (c) lipase-interesterification, (d) traditional chemical methods or (e) genetic manipulation. They are particularly useful because of the way in which they are metabolized. Specific fatty acids can be attached to specific portions of the glycerol backbone to ensure that those fatty acids are absorbed at specific portions of the digestive process.
For example, Norvartis Nutrition of Minneapolis, Minn. manufactures a nutritional product, named IMPACT.RTM., which includes structured lipids. IMPACT.RTM. contains randomized structured lipids formed by interesterification of palm kernel oil and sunflower oil. IMPACT.RTM. also contains fish oil, present as part of a physical blend. IMPACT.RTM. does not contain any fish oil that is part of a structured lipid. It is used for post surgical patients and sepsis patients. IMPACT.RTM. does not contain hydrolyzed proteins and would not be considered an elemental nutritional.
As another example, U.S. Pat. No. 5,661,180 to DeMichele, et al., describes a structured lipid which provides substantial benefits in terms of modifying the prostanoid synthesis pathway, resulting in an improved response to endotoxic shock and other stress states. This structured lipid includes three components formed on a glycerol backbone. The first component is either alpha-linoleic acid or dihomogamma-linoleic acid. The second component is a medium chain (C.sub.6 -C.sub.12) fatty acid residue and the third component is a C.sub.18 -C.sub.22 fatty acid residue.
A problem associated with elemental diets is their palatability. A hydrolyzed protein system typically provides an extremely bitter taste. Traditionally, most elemental products are tube fed and thus in these environments the unpalatable taste is not an issue.
However a large unmet need exists in the medical community for an elemental diet that can be consumed conventionally by drinking the formula. As noted above, recent evidence has shown that feeding by the enteral route provides a number of benefits to the patient. Dietitians have given patients with malabsorption syndromes elemental nutritional products and requested that the patient drink the elemental product. The volume the patient is being requested to consume is typically quite large. It can range from at least 250 ml up to 1500 ml, if the patient is relying upon the nutritional beverage as their sole source of nutrition. Despite the benefits that such a feeding regimen would provide, the vast majority of patients are unable to drink sufficient quantities of these elemental products to maintain their nutritional status. The unpalatability of these elemental diets invariably leads to substantial noncompliance issues. The noncompliance invariably leads to malnourished states or exacerbation of their underlying disease states if they attempt to resume a normal diet too early. Any attempt to additionally incorporate marine oil into an elemental diet will further exacerbate palatability issues.
U.S. Pat. No. 4,963,380 to Schroeder, et al., is directed to stabilizing fish oil against degradation. The reference specifies that fructose can be used for such a purpose. At column 4, lines 60-65 it specifies that sucrose was not such a stabilizer.
European Patent Application 0 296 116 discloses a suspension containing marine oils. The palatability of marine oils is increased by utilizing a three component system designed to increase the palatabilty of the marine oil. It includes an inorganic complexing agent, a sensory masking agent, and a sweetening agent. Sweetening agents include amino acid sweeteners, dipeptide sweeteners, etc. Sensory masking agents are flavored oils. Texturizing agents can optionally be included and preferably are not sweet. They are included to improve mouth feel. Crystalline sucrose is one possible texturizing agent. Sucrose is not identified as improving the flavor of fish oil products.
Thus, a need has developed in the art for an elemental nutritional product having improved palatability. Particularly, a need has developed in the art for a liquid nutritional product which incorporates soy protein hydrolysate in conjunction with hydrolyzed caseinate to provide essential nutrients in an easy to digest form. A further need has developed in the art for elemental liquid nutritional products which incorporate structured lipids to provide targeted delivery of essential fatty acids. Further a need has developed in the art to develop elemental nutritionals having improved flavor so that the product may be orally consumed (dranken) rather than tube fed to patients with malabsorption syndromes.